1. Field of the Invention
The present invention relates to a mobile communication system. More particularly, the present invention relates to a method and apparatus for supporting Non-Access Stratum (NAS) communication between a User Equipment (UE) and a Mobility Management Entity (MME) efficiently by addressing the signaling problems occurring between the UE and MME in a situation where it is necessary for a network node to identify the UE and acquire UE information, if there is any, from another network node to which the UE have been attached after a movement between two different Radio Access Technologies (RATs) such as Evolved Universal Terrestrial Radio Access Network (EUTRAN) and Universal Terrestrial Radio Access Network (UTRAN) or Global System for Mobile Communications (GSM)/Enhanced Data Rates for GSM Evolution (EDGE) Radio Access Network (GERAN).
2. Description of the Related Art
As one of the representative mobile communication standard organizations, the 3rd Generation Partnership Project (3GPP) has defined Evolved Packet System (EPS) with the introduction of MME.
The NAS protocols for the 3GPP 3G system have been revised in order to meet the requirements of high-speed data transmission in the next generation mobile communication system. The revision also has included backward compatibility to the 2G and 3G networks of 3GPP. In detail, when attaching to a network or updating a tracking area, the UE identifies the network node which it has accessed before using the node identity information of the UE identifier.
In a carrier network of the related art, however, the network is configured using even the bit information indicating network node identity information, and thus there is no room to distinguish between the legacy network mobility management node and the MME introduced for supporting the EUTRAN, resulting in a node identification failure problem. There is therefore a need of a method for improving communication service quality by minimizing processing delay with the provision of the information for the UE to discover the network node to which the UE has attached before and the acquisition of the UE information based on the provided information in the communication between the UE and the network through modification of the NAS protocol or a certain procedure of the UE or the mobility management node.